What is music21?

Music21 is a set of tools for helping scholars and other active listeners answer questions about music quickly and simply. If you’ve ever asked yourself a question like, “I wonder how often Bach does that” or “I wish I knew which band was the first to use these chords in this order,” or “I’ll bet we’d know more about Renaissance counterpoint (or Indian ragas or post-tonal pitch structures or the form of minuets) if I could write a program to automatically write more of them,” then music21 can help you with your work.

How simple is music21 to use?

Extremely. After starting Python and typing "from music21 import *" you can do all of these things with only a single line of music21 code:

Display a short melody in musical notation:
converter.parse("tinynotation: 3/4 c4 d8 f g16 a g f#").show()

Print the twelve-tone matrix for a tone row (in this case the opening of Schoenberg's Fourth String Quartet):
print (serial.rowToMatrix([2,1,9,10,5,3,4,0,8,7,6,11]) )

or since all the 2nd-Viennese school rows are already available as objects, you can type:
print (serial.getHistoricalRowByyName('RowSchoenbergOp37').matrix() )

Convert a file from Humdrum's **kern data format to MusicXML for editing in Finale or Sibelius:

With five lines of music21 code or less, you can:

Prepare a thematic (incipit) catalog of every Bach chorale that is in 3/4:

catalog = stream.Opus()
for workName in corpus.getBachChorales():
  work = converter.parse(workName)
  firstTS = work.flat.getTimeSignatures()[0]
  if firstTS.ratioString == '6/8':

Google every motet in your database that includes the word ‘exultavit’ in the superius (soprano) part (even if broken up as multiple syllables in the source file) to see how common the motet's text is:

import webbrowser
for motet in listOfMotets:
  superius = motet[0]
  lyrics = text.assembleLyrics(part)
  if 'exultavit' in lyrics:'' + lyrics)

Add the German name (i.e., B♭ = B, B = H, A♯ = Ais) under each note of a Bach chorale and show the new score:

bwv295 = corpus.parse('bach/bwv295')
for thisNote in bwv295.flat.notes:

Of course, you are never limited to just using five lines to do tasks with music21. In the demos folder of the music21 package and in the sample problems page (and throughout the documentation) you’ll find examples of more complicated problems that music21 is well-suited to solving, such as cataloging the rhythms of a piece from most to least-frequently used.

Music21 builds on preexisting frameworks and technologies such as Humdrum, MusicXML, MuseData, MIDI, and Lilypond but music21 uses an object-oriented skeleton that makes it easier to handle complex data. But at the same time music21 tries to keep its code clear and make reusing existing code simple. With music21 once you (or anyone else) has written a program to solve a problem, that program can easily become a module to be adapted or built upon to solve dozens of similar (but not identical) problems.

Interested in learning more?

Latest music21 News

How can I contribute?

Music21 is a rapidly-progressing project, but it is always looking for researchers interested in contributing code, questions, freely-distributable pieces, bug fixes, or documentation. Please contact Michael Scott Cuthbert (cuthbert at, Principal Investigator.

The development of music21 has been supported by the School of Humanities, Arts, and Social Sciences at M.I.T., the Music and Theater Arts section, and generous grants from the Seaver Institute and the NEH/Digging-Into-Data Challenge. Further donations to the project are always welcome.